Pump with pressure actuated reservoir



June 15, 1965 F. c. HABERLANKZE 3,188,965

PUMP WITH PRESSURE ACTUATED RESERVOIR Filed July 17, 19 2 Sheets-Sheet 1 I!" m w RN Q n a h .3 M Q a h mm 1 1 w E M Q a wfi a 1 mw n a u f L i| 6 u \N 1 n\ J E Iv f Q m M w h J a Q R g g: INN hm .Qw NM \Mm QR June 15, 1965 F. c. HABERLAND 3, ,9 5

PUMP WITH PRESSURE ACTUATED RESERVOIR Filed July 17, 1963 2 Sheets-Sheet 2 fnuerzz of" United States Patent Illinois Filed July 17, 1963, Ser. No. 295,714 3 Claims. (Cl. 103-39) This invention relates to hydraulic systems and more particularly to an improved pump including a pressure actuated reservoir.

The type of apparatus forming the subject matter of the present invention is commonly referred to as a hydraulic power supply package and comprises an appropriate prime mover, which may be an electric motor, hydraulic motor, or turbine drive, a variable displacement piston pump or fixed displacement gear pump, a reservoir, and miscellaneous filters, control valves, connectors and other auxiliary equipment needed to meet the system specification. In installations such as aircraft and missiles, these hydraulic power packages are operated only intermittently and consequently, are often required to be stored or maintained in a non-operating condition for long periods of time. However, when the pump motor is energized, it is essential that the desired flow and pressure characteristics are obtained immediately after start of operation. This means that the pump and its associated controls must be extremely reliable.

This requirement referred to above imposes some severe design limitations on the hydraulic supply package. First of all, sufficient hydraulic fluid must be maintained in the system even after long periods of storage. Secondly, the inlet fluid pressure must be at least at a predetermined minimum value for start-up (approximately 1 to 7 p.s.i.). Immediately after start-up, the inlet fluid pressure must be rapidly increased to provide full capacity, if required. Inasmuch as it is impractical to provide means for maintaining inlet fluid pressure at a level permitting full capacity (approximately 50 psi.) when the pump is not running, it is nevertheless essential that this inlet pressure level be reached as soon as possible after the ump begins operation. Accordingly, it is an important aspect of the present invention to provide a reservoir for the hydraulic fluid which is actuated in response to the discharge pressure of the pump to quickly develop suflicient inlet pressure immediately after starting operation of the pump.

It is therefore a principal object of the present invention to provide an improved hydraulic power supply package including a reservoir which maintains an adequate amount of hydraulic fluid in the system and supplies the required hydraulic pressure during operating and static conditions.

Other and more particular objects and advantages will be apparent from a reading of the following specification in conjunction with the appended drawings wherein:

FIGURE 1 is a schematic representation of a hydraulic system incorporating a hydraulic power sup ly package embodying the present invention;

FIGURE 2 is a cross-sectional view of a hydraulic power supply package illustrating the relevant details of the pump and reservoir assembly;

FIGURE 3 is a detail View, partly in section, illustrating the construction of one of the reservoir actuating pistons and the manner in which the pistons are connected to the movable reservoir shell; and

FIGURE 4 is a cross-section view taken along the plane of line 4-4 of FlGURE 2.

Turning now to FIGURE 1, this drawing represents, in schematic form, a typical hydraulic system adapted to utilize a hydraulic power supply package of the type forming the subject matter of the present invention. That portion of the system which is referred to as the hydraulic power supply package is shown within the dotted lines in FIGURE 1 and designated generally by the reference numeral it Regarding the hydraulic system in its entirety, it includes a pump 11 having an inlet 12 and an outlet 13, said pump adapted to be driven by motor 15. The pump 11 supplies fluid under pressure from its outlet 13 through line 14 which may include a filter element 24, to control means 16. The latter may comprise a servo-valve adapted to selectively supply fluid to a load 17 through lines 18 and 19. A return line 2h is provided from control means 16 to the pump inlet 12. The system further includes fluid reservoir means 21 fluidily interconnected with the pump inlet, said reservoir being actuated by fluid at discharge pressure through line 22.

It wiil be noted that the system shown in FIGURE 1 forms a closed circuit. Consequently, once the system is filled with hydraulic fluid, a minimum pressure available for start-up is maintained by resiliently loading the movable reservoir shell 23. This static condition pressure is preferably on the order of l to 7 p.s.i. which insures an adequate supply of fluid to the pump inlet for initiating operation of the pump. When the pump is energized, fluid at discharge pressure is supplied through line 22 and is effective to decrease the volume of the reservoir and thereby increase the inlet pressure level to a value permitting full capacity of the pump, said pressure level be ing on the order of 50 p.s.i.

It should be understood that the load 17 is merely representative of any device requiring a supply of hydraulic fluid such as, for example, a hydraulically operated actuating mechanism. Moreover, while certain, rather specific types of prime movers, pumps, and other components are referred to in this specification, it will be apparent that other equivalent components may be subsituted without departing from the teachings contained herein.

Referring now to FIGURE 2, the pump 11, in a preferred embodiment of this invention comprises a rotating cylinder barrel in combination with a swash mechanism. The specific details of this pump form no part of the present invention; however, insofar as it cooperates with the reservoir, its general design and operation will be described in connection therewith. It will be seen that a casing 30 is provided comprising two mating sections 31 and 32 which, for convenience, will be referred to as the body and cover respectively. The body 31 is provided with a central cavity 34 in which is disposed the working portions of the pump designated generally by numeral 36. At one end of the cavity, the pump body 31 is provided with a central bore 37 through which a drive shaft 38 extends. The drive shaft is journalled for rotation in ball bearing 39 which includes an outer race 4t) supported within a counterbore at one end of the cavity.

The drive shaft 38, driven from the motor through a connecting means (not shown), is provided with a series of external gear teeth 42 cooperating with a constant velocity universal joint mechanism 44 driving the cylinder block 46. The head of the drive shaft 38 includes a plurality of spherical pockets 45 forming seats for a series of piston elements 48. The other end of each piston is received within a plurality of cylinder bores 47 in the cylinder block 46. The drive shaft 38 is further provided with a blind bore 49 in which is received a spring assembly 59 engaging a pivoted rod 51 cooperating with the cylinder block 46. This spring assembly 50 serves as a limit stop for the pivoted cylinder block and also urges the cylinder block against the port block face which will be described in greater detail below.

The cylinder block 46 is rotatably supported within a cylinder barrel pivot assembly 54 which is pivoted in position wherein the axis of rotation of the cylinder block 4-6 is substantially co-axial with the axis of rotation of the drive shaft 38. V J a The pump cover 32, mating with the pump body 31, is provided with an arcuate slot slidably. receiving a,

complementary arcuate projection 56 from the port block I 60 which is fixed to the cylinder barrel pivotl assembly 54. The port block 60 includes a port face 61 engag-.

ing the-cylinder block face 62. The port block is further provided'with a kidney-shaped inlet port (not shown) which is in fluid communication with the interior of cav 4 of the pistons 75 and the interior ofjthe reservoir 21.

Fluid passage78 interconnects discharge passage with the high pressure side of the pistons in a manner which will'be discussed with more particularity in connection with FIGURE 3. 7 The reservoir 21 comprises a cylindrical, fixed shell fltL which .is secured by suitable means such as cap 'screws'81 to a fiange 83 on the pump body, and a cylindrical, domed, movable shell 85. A flexible, bellowstype seal 86 connects a flange a on fixed shell 80 with a corresponding flange a onthe movable shell 85 to providea variable volume chamber 88 which is fluidly interconnected with the interior of the pump cavity 34 j through fluid passage means 89.

ity 34 and a kidney-shaped discharge port 63 which communicates with a discharge passage means: 65 in the pump cover 32. To provide a sealbetween the pumpr cover and the port block 60, a slipper element 67 is disposed within the discharge port 63 and is urged into engagement with the adjacent portion of the pump cover 1 by a coil spring 69. I I I The drive shaft 38 drives cylinder block 46 through the constant velocity universal joint mechanism 44. As one of the cylinder bores passes by the inlet port in the port block, the fluid is drawn into the cylinder bore by the coordinated withdrawal of the piston. As the cylinder block rotates, the pistonrpasses through a deadcenter position, reverses direction, and as. the cylinder bore passes by the kidney-shaped discharge port,,fluid is discharged through apertures in the slipper element 67 and into the discharge passage 65. The displacement of the pump is controlled by varying the strokeyot the pistons through change in the swash angle between the cylinder barrel and the drive. Theswash angle may be defined as the angular displacement between the axis of the cylinder barrel and the drive mechanism; ,In the position shown in FIGURE 2, the swash angle issuch that a maximum displacement is obtained, and as the cylinder block is moved'to a position'wherein the respective axes of rotation of the cylinder block and the drive shaft are coaligned, the displacement approaches zero.

Means may be provided for automatically controlling the displacement of the pump in response to the load imposed on thesystem. Again, the specific details of the mechanism provided for this purpose, in apreferred embodiment of this invention, do not form an essential part of the pump mechanism and will be described only briefly. As shown in FIGURE 2,a'piston 64 is slidable Within a piston bore in the pump cover. acting through the connectingrod 66, is eliectiveto pivotthe cylinder block pivot assembly to vary the displace ment of the pumpin the manner described above. Movement of the piston 64 is controlled by the position of a spool valve 68 which is actuated by the pressuredifferential between'inlet and outlet. As discharge pressure is increased, fluid at an intermediate pressure is supplied to thepiston 64 to move the same in a'direction to decrease the displacement of the pump.

As indicated in the introductory remarks, animportant aspect of the present invention is the provision of a reservoir," indicated generally by numeral 21, which is adapted to increase the inlet pressure upon the actuation The piston,

" As best illustrated in FIGURES 3 and 4, the pistons are rigidly connected to a lock ring 90 by a series of screws or bolts 91. The lock ring 90 is provided with radially extending tabs or cars 93 which are adapted to be received within complementary: slots 92- in a ring 94 p which is brazed or weldedv to the rnovable shell 85. It will be noted that ring 94 is interrupted by recesses 96 spaced around the inner edgethereof. The radially extendingears 93 on the lock ring are similarly spaced around its circumference. When the unit is assembled,

the reservoir shellstructure 80, 85, carrying ring 94, is

positioned over the lock ring 90 so that the tab portions'93 are received within recesses 96. As" the shell structure is rotated through. an angle of approximately 60, the tab portions 93'are slidably received within the slots 92 in ring 94 to provide a disconnectable coupling arrangement. The assembly is completed by bolting fixed shell 80 to the pump casing.

This arrangement, whereby" the lock ring 90 is securely boltedto, the pistons 75,has several advantages. Since the threepistons are, in effect, formed into a single rigid unit by this technique, this allowstesting for freedom of movement prior to installing the reservoir. The lock ring engages the grooved ring brazed to the reservoir through the bayonet-type slots. The bearing area anc' rigidity are greatly increased; and the-reliability is alsc improved, because if one'or'two pistons momentarily stick, the other piston or, pistons can act through the lock ring to overcome the static friction of the sticking piston. Under. storage conditions, when the bellows springforce is required to maintain a static pressure 0: 1 to 7. psi, the'lock ring directs the spring force to ac along the center of the reservoir. Thus,-if one piston ha: high friction, it applies a larger portion of the spring fore to that piston so as to maintain a unifiorni storage ant inlet pressure. This is very important when the ambien temperature drops a few. degrees, requiring the bellow to move'the pistons a few thousandths of an inch to com pensate for the fluid contraction} 'Details 'of the cylinder and piston construction to the reservoir actuating'nrechanism are shown in FIGURl 3. It will be noted that fluid passage means 100 corn to discharge passage '65. The cylinder liner'or sleeve 71 of the pump. It will be notedthat the pump body 31 v is provided with a plurality of bores 70, preferably about three, extending generally parallel'with the axis of rotation of the drive shaft and cooperating with a series of complementary bores 72 formed in' the pump cover 32. a.

Each of the bores 70 is provided with a cylinder liner or sleeve '73 receiving one of 'a series of axially extending pistons 75' slidable therein. Fluid passages 76pmvide fluid communication between the low pressure side includes a terminal portion 101 which is provided wit] a series of apertures 10 3. Clearance' 104 is provide 1 between the piston stem 105 and the portion 101 of th sleeve. An O-ring'seal 106 is received in a groove i: the terminal portion 101 of the sleeve. Fluid at discharg pressure then passes through fluid passage means 7% connecting passage 100,- and apertures 103 into the cleai (ance space 104. Pressure is then available to act 0 the right hand face 108 (as viewed in FIGURE 3) c the piston head 110. I Operation As" mentioned previously, the system for which th hydraulic power supply package of the present inventio is adapted is a'closed system. Accordingly, the syster is initialyfilled with hydraulic'fluid so that the reserve: shell 851s fully extended and in the position shown i FIGURE 2. The Spring bias provided by the bellows seal 86 is sufiicient to maintain an inlet pressure of approximately 1 to 7 p.s.i. under static conditions. The main fluid inlet 12 communicates with the interior of the cavity 34 through fluid passage means (not shown) in the pump body. It will be remembered that the inlet port (not shown) in port block 60 is open to the interior of the cavity and therefore to inlet pressure. The main fluid outlet 13 is (not shown in FIGURE 2) inter-connected with discharge passage means 65. It should be understood that passages 65 and 78 are, in a sense, schematic insofar as they do not necessarily indicate the exact position of the flow path through the pump cover.

Upon energization of the motor, the pump begins operation and draws the hydraulic fluid from the pump cavity 34, which is filled with fluid, into the inlet port and the port block 60. Fluid at discharge pressure is supplied through passages 65, 78 and apertures 103 into the cylinder sleeve 73. This pressure acts against the piston heads 110 and immediately causes contraction of the reservoir through piston rods 75, the lock ring 90, and the slotted ring 94. As the movable shell 85 is moved to the left (as viewed in FIGURE 2), the inlet pressure is increased. As the pressure of the fluid within the reservoir is increased, this simultaneously increases the pressure of the fluid within the pump cavity 34 by means of fluid passage 89 which provides communication between the reservoir,

and the cavity, and consequently, the inlet port.

Having thus far described the basic features of the invention, it should be obvious that there has been provided an improved pumping system which is adapted to operate under depressed inlet conditions as outlined generally in the preliminary remarks. While this invention has been described in connection with certain specific embodiments thereof, it is to be understood that this is by Way of illustration and not by way of limitation; and the scope of this invention is defined solely by the appended claims which should be construed as broadly as the prior art will permit.

' What is claimed is:

1. A hydraulic apparatus comprising a pump having a casing, an inlet and an outlet; a first shell connected to said casing; a second shell connected to said first shell and telescopically received therein, said shells and said casing defining a variable volume fluid reservoir which is in fluid communication with said pump inlet; means defining a plurality of spaced cylinder bores within said casing; a lock ring member removably connected to said second shell; a plurality of piston elements each having one end secured to said lock ring member and the other end received within said cylinder bores; and fluid passage means interconnecting said pump outlet to said cylinders such that said piston elements are withdrawn into said casing and collapse said second shell into said first shell to increase fluid inlet pressure upon increasing fluid outlet pressure as applied through said fluid passage means.

2. A hydraulic apparatus comprising a pump including a casing, an inlet and an outlet; a first shell connected to said casing; a second shell telescopically received within said first shell; a resilient seal element connecting said first shell to said second, said shells and said casing defining a variable volume fluid reservoir which is in fluid communication with said pump inlet, said seal element biasing said second shell toward said casing; means defining a plurality of spaced cylinder bores within said casing; a lock ring member removably connected to said second shell; a plurality of piston elements each having one end secured to said lock ring member and the other end received within said cylinder bores; and fluid passage means interconnecting said pump outlet to said cylinders such that said piston elements are withdrawn into said casing and collapse said second shell into said first shell to increase fluid inlet pressure upon increasing fluid outlet pressure as applied thnough said fluid passage means.

3. A hydraulic apparatus comprising a pump including a casing, a fluid working space in said casing and an inlet and an outlet communicating with said fluid working space; a first, generally cylindrical, shell having one end connected to said casing, said first shell having a radially in-turned flange at its opposite end; a second cylindrical shell having a radially outwardly extending flange at one end and a dome shaped end wall at the opposite end thereof; a bellows-type seal element connected to the inturned flange of said first shell and the outwardly extending flange of said second seal, said shells and said seal element cooperating with said casing to provide a variable volume fluid reservoir in communication with said pump inlet; said seal element being resilient and biasing said second shell toward said casing; means defining a plurality of substantially equally spaced cylindrical bores arranged in parallel relation with respect to the axes of said shells; a ring member secured to said second shell adjacent said dome shaped end wall, said ring member having a plurality of slots defined therein; a lock ring having radially extending tabs mutually engageable with said slots to provide a detachable connection between said lock ring and said ring element; a piston element received within each of said cylindrical bores having a rod portion extending therefrom and connected to said lock ring; and fluid passage means between said cylindrical bores and said pump outlet arranged to apply fluid discharge pressure on one side of said piston elements to telescopically retract said second shell within said first shell to reduce the volume of said fluid reservoir upon increasing discharge pressure.

References Cited by the Examiner UNITED STATES PATENTS 2,745,357 5/56 Strayer 103-223 2,764,999 10/56 Stanbury 138-31 2,809,596 10/ 57 Sullwold et al 103223 LAURENCE v. EFNER, Primary Examiner. 

1. A HYDRAULIC APPARATUS COMPRISING A PUMP HAVING A CASING, AN INLET AND OUTLET; A FIRST SHELL CONNECTED TO SAID CASING; A SECOND SHELL CONNECTED TO SAID FIRST SHELL AND TELESCOPICALLY RECEIVED THEREIN, SAID SHELLS AND SAID CASING DEFINING A VARIABLE VOLUME FLUID RESERVOIR WHICH IS IN FLUID COMMUNICATION WITH SAID PUMP INLET; MEANS DEFINING A PLURALITY OF SPACED CYLINDER BORES WITHIN SAID CASING; A LOCK RING MEMBER REMOVABLY CONNECTED TO SAID SECOND SHELL; A PLURALITY OF PISTON ELEMENTS EACH HAVING ONE END SECURED TO SAID LOCK RING MEMBER AND THE OTHER 